The present invention is directed generally to a computer or chassis box structure for holding a plurality of computer printed circuit board assemblies. More particularly, the present invention is directed to a computer chassis structure for holding a plurality of computer printed circuit board assemblies in which all of the connectors at one side of each of the printed circuit boards are engaged to their corresponding connectors upon the attachment of a frontplane structure.
As computers become more and more powerful and require more and more memory, and particularly in the case of computers which operate on a plurality of data in a parallel manner, it has increasingly become necessary to interconnect larger and larger circuit boards to each other. Due to the complexity of circuitry that can now be mounted on a large printed circuit board, there can be hundreds, if not thousands of interconnections that must be made to each printed circuit board.
In the past, these interconnections have been accomplished by using either edge connectors at one edge of the printed circuit boards which plug into the appropriate connector mounted in a backplane, or by the use of multi-pin connectors mounted directly to the surface of the printed circuit board. Those multi-pin connectors plug into the corresponding multi-pin connectors mounted on the backplane. While in the past, such circuit board interconnections were sufficient, those interconnection systems no longer suffice in today's computing environment, particularly where a plurality of relatively large-sized printed circuit boards are being utilized.
In addition, in computer equipment in which the processing times are very fast, such as on the order of 40 megabits per second, there is a need to maintain as short an interconnecting path as possible between the components on each of the printed circuit boards that communicate with each other. For example, the electrical path from a component mounted on the half of the printed circuit board farthest away from the backplane connector must travel at least half the length of the printed circuit board before it even reaches a connector for that circuit board and can be transferred through the backplane to the appropriate circuit board which holds the component which is the destination of that signal.
Thus, the prior art devices have occasionally utilized connectors mounted to the opposite end of the printed circuit board not inserted into the backplane. They have utilized computer ribbon cables to connect between such connectors on adjoining or non-adjoining printed circuit boards. However, the use of such ribbon cables is disadvantageous because it increases the electrical path the signals flowing between these circuits must travel and it creates an additional step required during manufacture of the computer equipment to attach such ribbon cables. In addition, each of the ends of the ribbon cable must be carefully attached to the connectors in the circuit boards.
U.S. Pat. No. 4,470,100 to Rebaudo et al. illustrates a variation on the use of ribbon cables and connectors to interconnect boards. Rebaudo et al. disclose a welded card cage assembly for mounting a number of printed circuit boards in a mutually parallel configuration. Each card is constructed to include a first set of connectors mounted to one edge of the card. Two frame members are mounted to the other end of the card and a pair of connectors is mounted to the frame pieces. A ribbon connector cable connects the cable connectors to the printed circuit board. A backplane containing a plurality of connectors is then assembled to the welded card cage assembly. The connectors on the backplane are designed to connect to the connectors attached between the frame on each printed circuit board.
The apparatus disclosed by Rebaudo et al. creates several problems. Firstly, the use of ribbon cable increases the path to be travelled by signals between printed circuit boards. Secondly, using that device, it is difficult to align the pin connectors on the backplane with the pin connectors on a plurality of printed circuit boards such that no pins are bent during the insertion of the backplane connectors into the printed circuit board connectors. Thirdly, the effort required when more than just a few printed circuit boards are involved is quite high, making it even more difficult to accomplish the actual insertion of the connectors of the back portion into the connectors of the printed circuit board. In addition, Rebaudo, et al. presents the same difficulties described above in connection with pin alignment.
U.S. Pat. No. 4,151,580 to Struger et al. and U.S. Pat. No. 3,992,654 to Springer et al. both illustrate a rack for mounting a plurality of parallel circuit boards. The back edge of each circuit board is connected to a motherboard while an opposite edge includes terminal pads which align with a respective one of a plurality of individual movable sets of connectors in order to form an input/output connection plane. Those systems, however, do not provide a single frontplane system in which all of the connections are readily made in a single action upon attachment of the frontplane.
U.S. Pat. No. 4,134,631 to Conrad et al. discloses a modular plug board system which is utilized for testing certain circuit modifications with, for example, a central processing unit of a computer. The modular plug board system is used for interconnecting an array of parallel circuit cards in a card cage. The plug board is attached to a card cage and is connected directly to each of the plurality of circuit boards by a plurality of wires connected to a plurality of contacts which are used by the circuit modifying devices to make contact with certain components on the printed circuit boards. The Conrad et al. device is not designed for use in production computer equipment nor is it designed to provide interconnections between the circuit boards and components on the circuit boards. In addition, this approach is complex and costly to implement.